Moved the Blog

For a while this blog was a mirror of the one I write on TypePad. It was useful to be able to compare the two systems, but TypePad has lots of features not found here, and most of the readers are going there anyway, so I am going to stop posting here for a while.

Please visit the other blog at herot.typepad.com/cherot.

Are Cellphones Safe on Aircraft?

This month's IEEE Spectrum has an article (Unsafe at Any Airspeed?) about the potential for radio frequency (RF) emissions from cell phones to interfere with aircraft naviagtion systems. The primary concern raised by the authors is the effect on GPS-enabled landing systems. While cellular phones do not intentionally emit RF in the GPS band, improperly designed cellphones, or properly designed cellphones operating in close proximity to each other can generate spurious radiation in the 1200-1600 MHz band used by GPS receivers. The authors conclude that at a minimum, the FCC and the FAA need to coordinate their testing and associated rules before removing the current restriction on cell-phone use.

Some interesting facts presented in the article:

• The authors (with the permission of the airlines) carried a specially instrumented laptop on board 37 passenger flights in the US. On each flight they noted at least one case of a passenger making a cellular phone call, including a few during the critcal take-off and landing phases.
• The Samsung SPH-N300 cell phone has been implicated in several "incidents" where the GPS receiver lost satelite lock. Similar problems have been reported with DVD players and other seemingly innocent devices.
• The current FCC prohibition on making phone calls in flight only applies to "cellular phones" which technically means phones operating in the 824-849 Mhz band. "PCS phones" operating in the 1850-1910 MHz band are legal to use during flight. (!) Of course I wouldn't want to try to explain the distinction to the flight crew or the authorities, and given what I read in the article I don't think I would want to use either one of them during take-off or landing.